Abstract

Combretum schumannii Engl. is a plant documented in traditional medicine system for treatment of headache, oedema and pneumonia in some areas of North Eastern Tanzania. In the present study, extracts from parts of this plant were assessed for antibacterial, antioxidant capacity and cytotoxic activities to establish rationale for its use in traditional medicine. Dried leaves, fruits, stem bark and roots of C. schumannii were extracted using  dichloromethane:methanol (1:1), acetone (100%) and aqueous ethanol (80%), to afford dry extracts that were tested for antibacterial activity against eleven standard strains of bacteria. Portions of the same extracts were further subjected to in vivo brine shrimp lethality test and antioxidant activity test using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging method. Phytochemical screening of extracts was done by using standard chemical tests. Extracts of leaves, fruits, stem bark and roots of C. schumannii showed antibacterial activity against all test organisms, namely, Bacillus anthracis, Bacillus subtilis,Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Enterococcus faecalis, Staphylococcus aureus, Salmonella typhi, Vibrio cholera, Mycobacterium madagascariense and Mycobacterium indicuspranii. All extracts that were tested exhibited no significant toxicity against brine shrimp larvae with LC₅₀ values ≥253.30 µg/ml. Cyclophosphamide was used as a positive control with LC₅₀ of 16.37 µg/ml. Furthermore, all the extracts showed mild to strong DPPH scavenging activity in which case ascorbic acid was used as a standard antioxidant. The present study indicated that extracts from the leaf, stem bark and roots of C. schumannii are safe for human use and that, this plant may be a good source of antimicrobial compounds worth further development.

Key words: Combretum schumannii, antibacterial, antioxidant, cytotoxicity, phytochemical screening.